Knot question

[TheTreeSpyder]

Knude one; i just let the 50% go, but you are right of course! And in proper line with a proper DBY; a little higher than a regular bowline. Mr. Ekka; i'd think you'd want to listen rather than argue with this particular person about knots... Though the used line point is a good one; but that begs the question of how used a rope one works with!

My main point is that the position of this bowline. It isn't just simply terminating at an anchor with full stress on it. Whereby the sheetbend of the bowline is taking a full measure of force. But rather, this bowline is off the main pull, around bark friction and settling back to bend the main/ Standing Part that is coming to the tree as an anchor; with the bowline's eye. This is not the same as a bowline bending the Standing Part with it's sheetbend. This also avails, the 'hiding' of the sheetbend part of bowline, behind bark friction; so that only the dual legs of the eye take a full hit. The tests were on bowlines more like the 1st pictured, not running bowline as the 2nd pictured. The different mechanics of the different 1st loaded bend and stretcn are different; so thereby their failure points IMLHO.

If we bend the Standing Part backwards we can then put 2x load on eye. But generally the Standing Part is more loaded than it's choke due to angles of pull IMLHO. If we pull teepee flat, we raise the tension of both parts, but still, the Standing Part would be more loaded than the Bowline eye in a choke. In this eye there are 2 legs of support, once again best if the SheetBend of Bowline is behind 'buffering' friction.

It is true that rope stretch can smack ya in the face; if line breaks/ releases etc. Also, you have to pull extra distance. But, that distance and force is stored in the rope. So tghe flip side/ good thing about the stretch is that if you have energy stored in it, and keep pulling; when the tree starts to pull; you can have both you and the tree pulling on it at some point. This works a lot better with a truck pull getting someone 'unstuck' in another vehichle. If the pull vehichle keeps pulling as rope is contracting; more pulling power is available IMLHO.

 

[knudeNoggin]

http://www.deepcreekyachtclub.com/WebPage/KnotStrength.html but it doesn't have a running bowline.

Hmmm, some dubious figures here; but no statement as to rope type.
(I.p., the dia. of the object the hitches were tied to will affect strength.)

http://www.ropeinc.com/ropetensilestrength.html general comment in 2nd paragraph.

Interesting reading, but inconsistent with much else. --surprising values for
working load, but I think yachting does tend to have higher figures. --rather
high reduction to get min.strength (a safe Rule of Thumb, I guess).

I know of one guy who repeatedly used a running bowline on vehicle pulls without a shackle and it broke where the two met, it's a high friction point.

Broke the main line, or the Bowline eye? (using a double-eyed knot should help
in both cases; but using metal, yes, helps more easily)

I must say I have attended a fair share of home-owner pull overs gone bad and see plenty of busted 3 strand.

Busted where--at the eye-on-standingpart point?
Any surprise re the rope size (i.e., did you think "well, of course this broke!"
or "I'll be darned--making a mental note of this!") ?

I have a 7/8" double braid pull rope for big gum trees.

Hmmm, be nice to try maybe a 5/8" HMPE line--much weight savings.

Run those numbers on my rope you get 20,460lb goes down to 15,345lb for aged rope ... down to 9,974lb for knots ... my vehicle is putting 5000lb of force on as it's a light 4wd and I'm around the 50% mark.

And that's good figuring to work with. Moreover, you really don't want to be
pressing the limits anyway.

FYI, here's a link to more recent testing of some kernmantle ropes:
www.caves.org/section/vertical/nh/50/knotrope.html
[Dave Richards Cord.Inst. 7mm/10.5mm/12.5mm break tests]
NB: the tables have the correct data; the graphs have swapped the data
for the 12.5/10.5 sizes (7mm is right).
Of course, in any of these reports, we don't know how the knots were tied
and set.

Thanks,
*kN*

 

[Ekka]

Well spydie, he asked where I was getting those figures so I answered, not really an argument.

But you are right, the wrap around the back of the tree will take some heat off the knot but what about the bend where the two rub?

Knudenoggin is an avid rope guy with solid experience in this field, well experienced in rope and knots, and access to lots of testing data.

What are the numbers on this? Also, what would you suggest the other end that is tied to the vehicle be (knot wise)?

And finally I have a have question that has never been answered very accurately .... cycles to failure? Obviously that depends on loads subjected as % of Breaking strength but what info is out there and what is considered a reasonable allowance to make for worn ropes?

I just cant find that darned info on the climbing line test, do you guys know of it?

 

[Ekka]

Well, that was an excellent link ... keep clear of the sheet bend eh.

What do you recommend for joining 2 ropes together ...

same dia?

different dia?

Any data on say, Zepelin Bend? I have usually 3 options, square knot, sheet bend (with extra wraps) and Zepplin bend.

What does HMPE stand for and in the shelf name what is it, tenex, just double braid from like Samson etc.

I use that large dia rope (and it is heavy) coz it is relatively cheap over here and it does get beat up, it is the felling rope.

This is a link to the guy who makes it locally here in Brisbane. http://www.ropeonline.com.au/default.aspx

But for example if I go to our Arb shop I'd be paying around $7 per metre for 5/8 samson stable braid http://www.arbor.com.au/index.php?cPath=23&osCsid=43b2f24f5af7486e910db09ad0e9bf6a

So I go for the cheaper but heavier stuff.

 

[TheTreeSpyder]

HM is High Modulus like Kevlar.

HMPE is High Modulus PolyEthelyne like Spectre/Dyneema.

The bend at the Standing Part by eye is key. So this is variable, not set like the bend of the knot itself. Notice how the Standing Part can actually be bent around backwierds to place a 2:1 on the eye (that is comprised of 2 legs of support anyway). But this isn't normal useage. Normal useage is that the running bowline has leverage over the Standing Part; not at angles where the Standing Part has leverage over the eye; like in 2/1 effect example. The Standing part pull here is like a tight horizontal clothesline, the eye of running bowline is like weight/pull placed on the clothesline; leveraging the clothesline to higher tension by bending it.

i think a type of 'tensionless' hitch is best on the truckside. Whereby the line travels around as large a round device as possible a few times, then exits to hitch off to yet another device- without bending the Standing Part. The only thing i think would be better in theory would be a type of double or triple noose / scaffold hitch whereby 1 turn on mount is taken and the line comes back around to take it's turns around the Standing Part's 'throat' as it comes into the mount. i think this has a firming effect to fortify and stabilize this area some; thus the seemingly consistently high test numbers. Note if even a RoundTurn is taken on mount before turns around the throat are taken, the effect is lost. i think that is because not enough tension force is in Bitters then to perform this task of firming throat. But, then that would have to have an opening to slip off after use, or would probably have to cut line after truck pull. Note, that in test setups that one end of line will be tested and the opposite will be an eye, or some kind of tensionless type hitching that doesn't bend it's own Standing Part. i've had good luck with a quick Pile Hitch here, but don't know the test numbers. Many hitches like this would also depend on the size of the host mount, and how it bent the line too.

 

[knudeNoggin]

Well, that was an excellent link ... keep clear of the sheet bend eh.

What do you recommend for joining 2 ropes together ...

same dia?

different dia?

Any data on say, Zepelin Bend? I have usually 3 options, square knot, sheet bend (with extra wraps) and Zepplin bend.

(Sorry to not be snappy on reply ... .)-:
Rosendahl's (Zeppelin) Bend, like Ashley's Bend (#1452), can accommodate some
difference in ropes. The sheet bend results linked to in that test were for kernmantle
rope of a certain nature. One can improve the security and ease of untying (but
worsen the slack-security) of this knot by making a simple follow-on wrap & tuck
of the end of the wrap-&-tuck rope (what makes the turn around the u-part/bight)
--just bring this end around the bight's leg it was just tucked against and up at
the tip of the bight part. This works with either version of the Sheet Bend (and I'll
note that it wasn't made clear which version was tested--ends on same side (the
so-called "right-handed" form) or on opp.sides ("left-handed")).
There are also many like knots, but these aren't presented in the literature. You
might try a Triple Lapp Bend, e.g. (untie by pulling bight legs apart). YMMV
As for relative strengths, I recall one fellow doing A-vs.-B knot testing with his
truck for force, and Rosendahl's Bend did okay, Ashley's a bit better. R's knot
has a nice *flat* profile for taking abrasion if dragged, but that might not be of
issue with many uses.

What does HMPE stand for and in the shelf name what is it, tenex, just double braid from like Samson etc.

"High-Modulus Polyethylene", and sometimes one sees UHMWPE for "ultra-high
molecular weight PE", which might be a newer variant of fully synonymous.
Brand names are Spectra & Dyneema, which have *models* within.
I think it'd be nice if some arborist could get the windfall of some discarded
marine-use HMPE rope of adequately beefy size, though there might be some
surprises from the lack of any stretch. It's supposed to be pretty tough stuff,
though it's interesting (and frustrating) to read contradictory/inconsistent info
about rope materials from different sources (e.g., from "UV has NO effect" to indications
that it does).

As for the Running Bowline, it might be that using a twin-eye knot would give
some better effect at the through-the-eye point (so, too, having metal there);
there are some references on strength of a choker hitch--is it 70% load onto
the legs? But then comes seeing just how the noose is set. In any case, I'll
wager that it's not the knot/bowline that is the weak point.

Hitching to the truck depends on what the attachment point is. There are many
eye knots that can be tied in the bight (since there might be more rope than needed,
and the excess will be at the truck end).

*kN*